Siloxane resins containing methyl and phenyl bonded to silicon and laminates



"Z' Batented, Sept. 1, 955

' SEOXANE "RESINSI CONTAININGEQND r-PHENYL. BONDED T SILICON ANDHEBAMI- A NATES Harold Ai. Clarlr, "Midlalid, assignor tii Dow 1 (Zih'ning' ('iorr'ioratioiifivlidland, Mich.; a corporation I of Michigan No Drawing. H Application February 3,1953,

Sefifil -N 0i 334,971

- 3; 'ciaimss'a (or. 154 -43) 'Thisinventionrelatesto new and tisefulsiloitane'resins. Specifically, this .nivention is concerned with organ- 'opolysiloxane' resinous conipositions consisting essentially of 4.5 to 17' mol p61 cent'diphenylsiloxa'ne, 22 m ss mol per cent monopheiiy1siloxane,"aiicl 40 Ste I65 mol per 7 cent mono-methylsiloxane. g

"f'Organo's'ilicon' resins have becomeT' well-known v and i" "widelyused as laminating resins in 'industryw Theyare characterized generally by excellent. electrical ,properties and h'igh" heatfstabilit'y, the latter characteristic particu- '"lar'ly' dilfer'e'ntiatiiig mention organic-resinous materials- Some of' the-"known, orgariosilicon resin compositionsp'resently'available are suitable for low-pressure "laminating operations, but unfortunately, theulaminates or articles formed therefrom are characteriied by such low mechanical strength; especially at high; temperatures,

that they are useless for most commercial applications.

Some of the'presentlyknown silicone resin compositions 'lfonn .excellent ..laminates with; sayy glass clotlis when 1 inolded'sati high...pressures.-(i.' es about 1,000 p s.- i.). How ever,- .these.resins. will not produce Iaminates-When rhi molded at low..pr.essure- (.i.-e., 3'0 pks. i. amass- 1 The value of forming-laminates at low pressure lies chiefly in the fact that it allows contour molding ,(i. e., the t'noldiii'gof "curved andirregular shapes). Theseshapes cannot be formed at high pressure. Thus, the resinous compositions of this invention make it possible for the first time to prepare commercially acceptable low-pressure silicone resin laminated articles.

It is the object of this invention to prepare resin compositions which are suitable for either highor low-pressure laminating operations. Another object is to provide silicone laminates which have flexural strengths heretofore unrealized.

Low-pressure laminates prepared with the organosilicon resins of this invention have mechanical strengths greater than high-pressure laminates prepared from heretofore known organosilicon resins. The improvements effected by using the compositions of this invention are obtained without sacrifice of other physical properties such as dielectric strength.

The advantages of the compositions of this invention are pronounced at elevated temperatures. For example, the flexural strengths at 260 C. of laminates using the resins of this invention are nearly twice those obtained using previously known silicone resins. This is important, since silicone resins are normally employed at temperatures above 150 C. Furthermore, the room temperature strength of laminates prepared from, the instant compositions does not deteriorate substantially after prolonged aging at 250 C.

The compositions of this invention are prepared by employing conventional and well-known means of cohydrolysis and co-condensation of hydrolyzable monomethyl, monophenyl, and diphenyl silanes. Thus, (CH3)SiCl3, CsHsSiCls, and (CsH)2SiClz may be separately hydrolyzed and then the resulting siloxanes cocondensed, or these silanes (in proper proportion) may r be cohyilrolyzed and .then turtherlcondiisedttdiiyield the 'resiris ofithis'invention. It! is tobeunders'toodithat other'silanessuch'asthe 'alkoiry silan'e's, may be employed in lieu of the aboveihalogenosilanes. Co-condensation I of the abovesiloxanes is best carried out-.imthe presence of conventional.siloxaneresincatalysts suchasnietal salts of-carboxylicacids and} quaternary .amrnoniuin salts. Laminates, prepared .from the resins of invention are"made employing conventional procedures. For exj ample, "a fabricinay be 'dip.- impregnated with rresin solu- I tionjair dried, and pre cu'red atflabou t 110 C.. treduce "resin flowfin'oldedlto desired, shapeunder heat and-.rpressure; and then after-baked to,' obtain desired, properties. Silicone resin laminates ofg'lass cloth are ordinarily afterbaked for 12' to' '48 hours' at 250 C. .111 orde iitdhasten "theycuretime "or the resin during: inolding catalysts may beadded' "to the 'resins of this invention. Y Suitable. cata- .lystsf include metal salts of carboxylic acids. suchlas .zinc

J "'oct ateqf potassium-weenie.

' Thecompositio'ns"of this invention and the preparation thereof are amply illustrated -in the following examples. It is to be understood,-however, thattno limitation is to 'be implied. therefrom. The scope'of this .invent ion is specifically 'and ..co'rrect1y set. forth in the-claims; The l'fleku'ralstrength values or. all laminateswere idetermined Z in ac cordance with -FederaL Specification foryBlastics,

-LP'-4'06A.-

" Example I I v :2 r Awimixture-tvof .65 mol percentine'thyltrichlorosilane and -mol 'per'e'entphenyltrich'lorosilanewas hyd iyzed n a .coldiwater-toluen'e mixture togive' a 27 per cent by .-.:i;.-weight tolueneisol ut-ion ofa"=resi-nou"s' copolymerof' "onomethylsiloxane't 'and monophenylsi-ldxane (i. hydrolyzate) To 900 grams of theabove resin (in the form of a 27 per c'ei it b weight s'olutio 'n' toluene)wasadded 100 "g'rams of cliphe'nylsila'iiediol. Then'iixturef'wasvacum strippedto l0 per centsolid Afte'r st-rippiii'g; the condensing catalyst; zinc o'c'toate;-- wa-= addedin a'niount sufiicient to give 0.1 per cent zinc based on the total resin weight. The mixture was heated at reflux for 3 hours, then cooled, filtered, and diluted to 60 per cent solids in toluene. The resulting resinous copolymer had a composition of 4.7 mol per cent diphenylsiloxane, 62 mol per cent monomethylsiloxane, and 33.3 mol per cent monophenylsiloxane.

To this resin copolymer dissolved as 60 per cent solids was added a condensing catalyst, trimethyl (beta-hydroxyethyl) ammonium 2-ethyl hexoate in amount of 0.22 per cent by weight based upon resin weight. A laminate of glass cloth and the above resin was formed in the following manner.

Commercial heat-cleaned glass cloth designated as ECC 181 was dip impregnated to 35 per cent resin (based on total weight of cloth and resin). The impregnated glass cloth was air dried for one half hour and pre-cured at 110 C. 14 layers of this pre-cured impregnated cloth were stacked to give a laminate. This laminate was heated for 30 minutes in a press at 175 C. under a pressure of 30 pounds per square inch. The resulting A" thick laminate was removed from the press and baked as follows: for two hours at 125 0, two hours at 150 C., two hours at 175 C., and two hours at 200 C. At the end of this heating, it contained 30 per cent by weight resin and per cent glass cloth. The laminate was tested by baking at 250 C. in an air oven. After 24 hours, the laminate was found to have a flexural strength at 260 C. of 18,000 p. s. i. After hours, it had flexural strengths of 18,200 p. s. i. at 260 C. and 44,250

70 p. s. i. at room temperature.

A laminate was prepared in identical manner using a commercially available low-pressure laminatingresin the octoate) based on resin weight.

having a' composition of 34 mol per cent monomethylsiloxane, 38 mol per cent monophenylsiloxane and 28 mol per cent dimethylsiloxane. After 24 hours at 250 C., the flexural strength at 260 C. was 8,500 p. s. i. After 125 hours at 250 C., it had flexural strengths of 12,500

p. s. i. at 260 C. and 30,000 p. s. i. at room temperature.

. Example 2 Following the procedure of Example 1, a resin copolymer having the composition of 10 mol per cent diphenylsiloxane, 58.5 mol per cent monomethylsiloxane, and 31.5 mol per cent monophenylsiloxane was obtained by co-condensing 800 g. of a methyltrichlorosilane-phenyltrichlorosilane cohydrolyzate and 200 g. of diphenylsilicondiol in the presence of 0.1 per cent zinc (added as A one-eighth inch thick 14 ply laminate of the glass cloth was prepared employing the above resin catalyzed with 0.27 per cent trimethyl (beta-hydroxy-ethyl) ammonium 2-ethyl hexoate, following the procedure used in Example 1. This lami- I nate, after aging for 125 hours at 250 C. was found to have a room temperature flexural strength of 42,500

, p. s. i., and a flexural strength at 260 C. of 18,900 p. s. i.

Example 3 inating step, the catalyst was 0.27 per cent trimethyl (beta-hydroxyethyl) ammonium 2-ethyl hexoate. After 125 hours aging at 250 C., the A; inch thick, 14 ply laminate had a flexural strength of 46,800 p. s. i. at room temperature and 16,000 p. s. i. at 260 C.

Example 4 'A laminating resin having a composition of 58 mol per cent monomethylsiloxane, 35 mol per cent monophenylsiloxane, and 7 mol per cent diphenylsiloxane was prepared in the following manner. 520 grams of CHaSiCla' 443.6 grams of of (CsI-I)zSiClz were added to a 5 liter reactor and 300 grams of isopropanol were slowly added over a period of 9 hours. The mixture of alkoxylated silanes was transferred to a separatory funnel and diluted with 600 grams of toluene and added slowly to a hydrolysis medium consisting of hot water, isopropanol, and toluene. After hydrolysis, the resin layer was transferred to a 5 liter reactor, admixed with grams of calcium carbonate, stirred for 15 minutes, filtered, and vacuum stripped to 64 per cent solids. Laminates prepared from this resin were easily molded at low pressure (e. g. 30 p. s. i.) and were characterized by excellent flexural strength.

Example 5 Employing the procedure used in Example 4, a resin copolymer consisting of mol per cent monomethylsiloxane, 15 mol per cent diphenylsiloxane and 25mol per cent monophenylsiloxane was prepared. This resin was found very effective for making low or high pressure laminates with glass cloth or molded articles containing asbestos, mica, or glass flock.

That which is claimed is:

1. An organosilicon resin copolymer consisting essentially of 4.5 to 17 mol per cent diphenylsiloxane units, 22 to 55 mol per cent monophenylsiloxane units, and 40 to 65 mol per cent monomethylsiloxane units.

2. An article of manufacture comprising fabric impregnated with the composition of claim 1.

- 3. A laminated article comprising at least two layers of fibrous material impregnated and bonded with the composition of claim 1.

References Cited in the file of this patent UNITED STATES PATENTS 2,258,222 Rochow Oct. 7, 1941 2,442,212 Rochow May 25, 1948 2,504,388 Braley Apr. 18, 1950 2 2,518,160 Mathes Aug. 8, 1950 FOREIGN PATENTS 133,541 Sweden Nov. 6, 1951' 

1. AN ORGANOSILICON RESIN COPOLYMER CONSISTING ESSENTIALLY OF 4.5 TO 17 MOL PER CENT DIPHENYLSILOXANE UNITS, 22 TO 55 MOL PER CENT MONOPHENYLSILOXANE UNITS, AND 40 TO 65 MOL PER CENT MONOMETHYLSILOXANE UNITS. 